If you've made your first purchase using the VIP option at checkout, you are now subscribed to the JustFab VIP Membership Programme. You'll be charged for a membership fee on the 6th of each month if you haven't shopped (no minimum purchase threshold) or 'skipped' the month by the 5th of the month. This charge will be stored in your account as a VIP Member Credit, which you can redeem against any item on the site.
If you want to avoid being charged for that month, simply log in to your account and click on the 'Skip the month' button by the 5th of the month. You can skip as many months as you like, and you'll still enjoy all your VIP perks. Find out more here.